Nowadays, hard disk drives (hereinbelow, referred to as HDDs) rotate magnetic disks and drive head gimbal assemblies (hereinbelow, referred to as HGAs) at high speed in response to requests for huge capacity, high recording density, and high-speed accessing. These cause fluctuation of air (turbulence) to buffet the magnetic disks and HGAs. This turbulence buffeting will be a big disturbance for positioning heads for data which are recorded with high-density on a magnetic disk. This is because the turbulence occurs at random and it is difficult to estimate its magnitude and cycle so that swift and accurate positioning control will be complex and difficult. Also the turbulence buffeting may cause a noise to impair the quietness of the device.
Another problem caused by influence of the air within the device due to the high-speed rotation other than the foregoing is increase of electric power consumption. When the magnetic disk is rotated at high-speed, the air around the disk is dragged and rotated together. On the other hand, the air apart from the magnetic disk remains still so that shearing force arises therebetween to become a load against the rotation of the disk. This is called as windage loss, which becomes larger as the disk rotates at higher speed. In order to rotate the disk at high-speed against the windage loss, a motor will require a larger output and electric power.
Focusing on that the above-described turbulence and windage loss are proportional to the density of the gas within the device, there is an idea to reduce the turbulence and windage loss by enclosing low-density gas instead of air in a hermetically-sealed HDD. Hydrogen, helium, or the like is exemplified as the low-density gas, but helium is optimum because it is effective, stable, and safe in considering actual use. HDDs with sealed helium gas can solve the above-described problems and realize swift and accurate positioning control, electric power saving, and satisfactory quietness.
However, molecules of helium are so small and a diffusion coefficient of helium is large. Therefore, there has been a problem that enclosures used for usual HDDs are poorly sealed so that helium gas leaks easily during normal use. In order to make it possible to hermetically seal low-density gas such as helium gas, for example, a technique disclosed in U.S. Patent Publication No. 2005/0068666 (“Patent Document 1”) described below has been suggested.
Helium gas is enclosed in an enclosure in manufacturing the HDD. For example, assembling components of the HDD in a chamber filled with helium gas results in enclosing helium gas in the enclosure. However, preparing such a chamber costs much and significantly reduces production capability. Therefore, an approach is considered to fill up helium gas in the enclosure: after assembling the components in the enclosure, injects helium gas under pressure through a hole on the enclosure while discharging the air in the enclosure through another hole. This approach accomplishes helium gas injection in a normal factory.
Thus, in the case that helium gas is injected into the enclosure by use of the injection hole and the emission hole, it is required to seal the injection hole after helium gas has been injected. Typically, the holes are sealed by attaching aluminum sealing tapes to the outer surface of the enclosure. However, if a certain time has elapsed from the helium gas injection until the attachment of the sealing tape, the helium gas injected within the enclosure will leak out so that the helium density within the enclosure will decrease. Or, if it takes time to inject the helium gas, throughputs in manufacturing HDDs will be reduced. Therefore, it is required to inject helium gas into the enclosure as quickly as possible to reduce the injection time.